Cellulose derivative and method of making the same



is present even in very small amounts at least some pyrosulfuric acid (HzSzOv or 112804503) will be present and the advantages of this invention realized.

In the preferred form of the invention chlorosulfonic acid and sulfuric acid are mixed with an inert diluent which may be dioxane or carbon disulfide and the mixture is then mixed with pyridine which may be dissolved in a solvent such as dioxane or toluene. The mixing takes place as the two streams of liquid unite while descending through a cooled tube. To the solution thus obtained cellulose is added and the mixture stirred with heating to a temperature of 70 to 110 C. until the desired properties are obtained. The product may be isolated by filtering from the diluent and by extracting with denatured alcohol or other liquid which does not dissolve cellulose sulfuric acid.

As starting material any of the ordinary varieties of cellulose may be used including wood pulp, cotton linters, hydroor oxy-cellulose, and partially substituted cellulose derivatives such as low substituted methyl cellulose or partially substituted cellulose acetate. Starch, inulin, glycogen, or other carbohydrates may be used in place of cellulose.

Instead of pyridine, other tertiary amines such as the picolines, lutidines, collidines, quinoline, ethylpyridine, conyrine, dimethylaniline, diethylaniline, tri-n-butylamine, dimethylcyclohexaylamine, etc., may be used. The temperatures of the reaction may be varied from room temperature to 130 C. although temperatures of from 'l5-90 C. are preferred. Where pyridine hydrochloride is formed as in the reaction of chlorosulfonic acid and sulfuric acid in pyridine solution lower temperatures may be used than in the case of oleum or pure pyrosulfuric acid. In the latter case temperatures of well over v C. may be used without danger of tarry by-product formation or degradation of the cellulose. The time of reaction varies with the temperature, the diluent, the reagents used, the degree of esterification desired, and the viscosity of product desired. Thus, by using C. less time is required for a given amount of esterication than at lower temperatures as for example 70 C. A diluent retards the rate of reaction and therefore longer time for esterication is necessary when using a diluent in order that a given extent of esteriflcation may be realized.

The amount of esterication varies with the product desired. If a completely water soluble product is wished esteriflcation is to be more complete than if a simple pretreatment oi the cellulose is desired. l The rate of reaction may be controlled by the catalyst, the diluent, the temperature and the proportion of reagents used. Suitable catalysts include pyridine hydrochloride or hydrobromide, ethylpyridinium chloride, benzylpyridinium chloride, quinoline hydrochloride, picoline hydrochlorides, lutidine hydrochlorides, and other agents which have a pronounced swelling action `on cellulose.

Inert diluents may be used in this reaction either to preserve the fibrous form of cellulose or to facilitate mixing during the reaction. The diluents are not essential and in the case of aleum and pyrosulfuric acids are not desirable.

Suitable diluents are chlorobenzene, benzene, l

toluene, dioxane, dibenzylether, di n butyl ethane, acetone, diethyl phthalate, etc.

In place of pyrosulfuric acid any of the ordinary equivalents may be used as, for example, mixtures of chlorosulfonic acid and concentrated sulfuric acid, oleum and concentrated sulfuric acid, phosphorous pentoxide and sulfuric acid, etc. The effect of varying proportions of reagents is illustrated by the following table.

TABLE I Eect of proportions of reagents Chloro- Percent No. Cellulose Pyridme Dioxane Sammie sulfuric H 04 in kilograms liter liter acid um. acid liter product 1 0. 45 4. 38 2. 40 l. 00 0 31. 2-- .45 4.38 2.40 .91 .08 34.6 3.- .45 4.38 2.40 .32 .l5 34.6 4-. .45 4.38 2.40 .73 .22 32.1 5.- .45 4.38 2.40 .64 .30 16.5 6.. .45 4.38 2.40 .55 .37 33.9 7..- .45 4.38 2.40 .45 .45 17.7 .45 4.38 2.40 .36 .52. 8.8 9-- .45 4.38 2.40 .27 .60 1.7 l0.. .45 4.38 2.40 .18 .67 2.2 ll.- .45 4.38 2.40 .09 .75 2.4 l2-. 45 4. 38 2. 40 0 82 3. 14

The combined amounts of chlorosulfonic acid and sulfuric acid is held constant at 5.5 mols. of SOsH per glucose u nit of the cellulose mol.

The Water soluble salts of the cellulose sulfuric acidof the present invention are useful as sizing materials, dispersing agents and as intermediates in preparing cellulose derivatives. Sheets and iilms may be prepared from this material for special uses.

The process of the present invention affords an ease of control both in mixing the reactants and in control of the final product which is new in the art of the preparation of cellulose sulfuric acid. By-product formation is largely eliminated with consequent saving in material and increased purity of product. The reaction `of pyrosulfuric acid on cellulose in the presence of pyridine takes place more rapidly than in the case of sulfur trioxide reacting with cellulose and more smoothly than in the case of chlorosulfonic acid reacting on cellulose in the presence of pyridine.

As disclosed in Table I. use of the proper proportions of acid and acid chloride permit more uniform and more complete esterication of the cellulose. In addition to these advantages which are obvious from Table I, the resulting cellulose sulfuric acid from the product disclosed in such reactions as No. 6, Table I, is much less degraded than the product'represented by No. 1, Table I.

' The derivative, moreover, is less contaminated by tarry by-products than any prepared by processes previously disclosed. In the prior art method of preparing cellulose sulfuric acid, the reagents used were either sulfur trioxide or chlorosulfonic acid. Each of these reagents is very hazardous and diicult to In the reaction of cellulose with chlorosulfonic acid even with ice cold pyridine there is the disadvantage that the pyridine tends to sulfonate in place of cellulose sulfuric acid being formed because of the exothermic character of the reaction between pyridine and chlorosulfonic acid. A further'diiliculty of this process is the tendency for the addition product of chlorosulfonic acid and pyridine to transform itself into colored and tarry by-products under the reaction conditions so that the cellulose derivative formed is contaminated with impurities.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it

is to be understoodl that I do not limit myself to 75 except as. de-

l. Process for the preparation of cellulose sul i furic acid comprising reacting cellulose with'pyrosulfuric acid in the presence 0i.' a.' tertiary amine.

2. Process for the preparation of cellulose suliuric acid comprising reacting cellulosel with a mixture of chlorosulfonic acid and concentrated sulfuric acid in the presence of a tertiary amine.

3. Process for the preparation of cellulose sulfurie acid comprising reacting cellulose with pyrosulfuric acid in the presence of pyridine.

4. Process for the preparationv oi' cellulose sulfuric acid comprising reacting cellulose with a mixture oi' chlorosuli'onic acid and concentrated sulfuric acid in the presence of pyridine.

5. Process for the" preparation of cellulose sulfuric acid comprising reacting cellulose with pyrosulfuric acid in the presence of a tertiaryamine at a temperature between 20 and 130 C.

6. Process for the preparation of cellulose sulfuric acid comprising reacting cellulose with pyrosulfuric acid in the presence of a tertiary amine at a temperature of between 75 and 90 C.

7. Process for the preparation of cellulose sul-.- furie acid comprising reacting forty-ve parts oi.' cellulose with the reaction mixture of thirty-seven parts by volume oi' 95% sulfuric acid and fiftyilve parts by volume of chlorosulfonic acid in the presence of 438 parts by weight of pyridine at 110 C. for two hours.

GEORGE W. RIGBY. 

